The invention relates to a telescopic cylindrical tube column able to be used in numerous fields such for example as radiology, where telescopic columns allow the X-ray emitting assemblies or detector assemblies which they support to be positioned.
These assemblies often form very heavy loads, connected to the telescopic column through an arm; this latter generally forms an angle of 90.degree. with a longitudinal axis of the telescopic column, about which it is able to rotate, for positioning the load; this arrangement tends to make even more difficult the working conditions of these columns whose rigidity is maintained because of their massive structure, taking up a relatively large space.
Telescopic columns are generally formed from several tubes of different sections, adapted to slide in each other through the presence of linear guide means disposed over the length of these tubes between each of them.
These guide means may comprise for example four rails provided between each tube, on the periphery of which these rails are disposed spaced apart by 90.degree.. One condition for proper sliding of the tubes resides in the parallelism of the rails; this parallelism is obtained by adjusting the position of these rails, such as adjustment of the parallelism of the first two opposing rails along a first axis of the section of a tube, followed by adjustment of the parallelism of the second rails situated on a second axis spaced at 90.degree. from the first one.
This represents a long and delicate operation which forms a disadvantage. Another disadvantage of this arrangement resides in the fact that it does not lend itself to the use of cylindrical tubes, which tends to further increase the space occupied by the telescopic column thus formed. It should also be noted that in operation, when the arm carrying a load passes through the first axis on which the first rails are located, only the guide means comprising the second rails are in a position to withstand the forces created by this load.
Another type of guide means comprises balls rolling between two tubes, in longitudinal grooves; these latter are situated opposite each other, on the one hand on the inner wall of a first tube and, on the other hand, on the outer wall of a second tube sliding in the first one.
The drawback of this arrangement is that no adjustment is possible, more particularly when play appears between the tubes due to the wear of the grooves.